function Hv = H(alpha,beta)
k=[cos(alpha)*cos(beta);
    cos(alpha)*sin(beta);
     sin(alpha)];

r{1} = [1/4 -1/4 0];
r{2} = [-1/4 -1/4 0];
r{3} = [-1/4 1/4 0];
r{4} = [1/4 1/4 0];

phi=nan(4,1);

for i = 1:4 
    phi(i)= 2*pi*r{i}*k;
end

Hv=exp(1i*phi);

end

